Hot mix asphalt (HMA) pavement refers to the bound layers of a flexible pavement structure. Asphalt pavement material is a precisely engineered product composed of about 95 percent stone, sand, and gravel by weight, and about 5 percent asphalt cement, a petroleum product. Asphalt cement acts as the glue to hold the pavement together. Our HMA is mixed at our asphalt production facilities located throughout northern New England.
Placed and compacted at elevated temperatures, hot mix asphalt pavements are typically applied in multiple layers, with the lower layers acting to support the top layer, known as the surface or friction course. The aggregates in the lower layers are chosen to prevent rutting and failure, while the aggregates in the surface course are chosen for their friction properties and durability. When designing a HMA pavement the aggregate used must be strong and durable, and have a good angular shape to help resist rutting. The fine aggregate (mineral filler) is used to fill in the voids between the coarse particles, which increases the density of the asphalt concrete and provides load transfer between the larger particles. The asphalt binder is typically 5-6% of the mixture, and serves to bind the aggregates together. Asphalt binder is a petroleum derivative, though additional materials are often added to modify the properties of the binder.